Hologram recording film and method of manufacturing same, and image display apparatus

ABSTRACT

A hologram recording film manufacturing method includes the steps of obtaining a laminated structure by alternately laminating M (where M≧2) photosensitive material precursor layers including a photosensitive material and at least one (M−1) resin layer on one another, obtaining M photosensitive material layers, where at least two interference fringes with a desired pitch and a desired slant angle are formed on each of the M photosensitive material layers, from the M photosensitive material precursor layers by irradiating the laminated structure with a reference laser light beam and an object laser light beam, and making the slant angles of the M photosensitive material layers different from each other while retaining the pitch value, which is defined on a face of the photosensitive material layer, by irradiating the laminated structure with an energy ray from the laminated structure&#39;s one face side, and heating the laminated structure.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of and claims the benefit ofU.S. patent application Ser. No. 12/633,475, filed on Dec. 8, 2009,which claims priority to Japanese Priority Patent Application JP2008-312837 filed in the Japan Patent Office on Dec. 9, 2008, the entirecontent of which is hereby incorporated by reference.

BACKGROUND

The present application relates to a hologram recording film and amethod of manufacturing same, and an image display apparatus.

Virtual image display devices (image display devices) using a hologramdiffraction grating so as to allow an observer to observe atwo-dimensional image generated through an image forming device as anenlarged virtual image through a virtual image optical system have beenmade public through, for example, Japanese Unexamined Patent ApplicationPublication No. 2007-11057.

The above-described image display device, that is, an image displaydevice 100 includes, for example, an image forming device 111 configuredto form and display an image, a collimating optical system 112, and avirtual image optical system (optical device 120) onto which a lightbeam emitted from the image forming device 111 is made incident and bywhich the light beam is led to eyes 60 of the observer. Here, theoptical device 120 includes a light guide plate 121, and first andsecond diffraction grating members 130 and 140 that are provided on thelight guide plate 121. A light beam emitted from each of pixels of theimage forming device 111 is made incident on the collimating opticalsystem 112, and the collimating optical system 112 generates a pluralityof collimated light beams that are made incident on the light guideplate 121 at angles different from each other, and the collimated lightbeams are made incident on the light guide plate 121. The collimatedlights are made incident and emitted from one optical face (first face)122 of the light guide plate 121. Further, the first and seconddiffraction grating members 130 and 140 are secured to the other opticalface (second face) 123 of the light guide plate 121, the optical face123 being parallel with the first face 122.

The collimated light beams that are made incident on the light guideplate 121 at the different angles from the first face 122 are madeincident on the first diffraction grating member 130, and each of thecollimated light beams is diffracted and reflected, as it is. Then, thediffracted and reflected collimated light beam travels while beingtotally reflected repetitively between the first and second faces 122and 123, and is made incident on the second diffraction grating member140. The collimated light beam which is made incident on the seconddiffraction grating member 140 does not satisfy the total reflectioncondition by being diffracted and reflected, and is emitted from thelight guide plate 121 and led to the eyes 60 of the observer.

Each of the first and second diffraction grating members 130 and 140includes a reflection-type volume hologram diffraction grating in whichinterference fringes are formed. Each of the first and seconddiffraction grating members 130 and 140 should be provided with a widediffraction wavelength band. Namely, three primary-color light beamsincluding a red light beam, a green light beam, and a blue light beamthat are emitted from the image forming device 111 should be diffractedand reflected. Consequently, the interference fringes formed in thereflection-type volume hologram diffraction grating are duplexed.Otherwise, multiple diffraction grating layers are provided.

Here, a Bragg condition for attaining diffraction and reflection in thediffraction grating member is expressed through Equation (A) thatfollows. In Equation (A), the sign m denotes a positive integer, thesign λ denotes a wavelength, the sign d denotes a pitch defined on agrating surface (which denotes an interval defined in the direction ofthe normal of a virtual plane including the interference fringes, and ishereinafter referred to as a “grating surface pitch”), and the sign Θdenotes the complementary angle of an angle at which a light beam ismade incident on the interference fringe. The slant angle (inclinationangle) φ of the interference fringes denotes an angle which the surfaceof the diffraction grating member forms with the interference fringe.The interference fringes are formed so as to extend from the inside thediffraction grating member to the surface of the diffraction gratingmember, as is the case with the following descriptions. Further, therelationships between the complementary angle Θ, the slant angle φ, andan incident angle ψ that are obtained when a light beam enters thediffraction grating member at the incident angle ψ are as shown inEquation (B), and illustrated in FIG. 10B. Further, the pitch Λ of theinterference fringes observed on the surface of the diffraction gratingmember is as shown in Equation (C). Hereinafter, the above-describedpitch Λ will be referred to as a “surface pitch” so as to bedistinguished from the grating surface pitch d. The surface pitch Λ isillustrated in FIG. 10B.

m·λ=2·d·sin(Θ)  Equation (A)

Θ=90°−(φ+ψ)  Equation (B)

Λ=d/sin(φ)  Equation (C).

SUMMARY

A method of generating diffraction grating layers (hologram recordingfilm) having different diffraction center wavelengths (reproductioncenter wavelengths) in advance and laminating the diffraction gratinglayers on one another while aligning the diffraction grating layers(referred to as a “first method according to a related art” forconvenience) has been adopted so as to manufacture a diffraction gratingmember including multiple diffraction grating layers having interferencefringes with different slant angles (inclination angles) φ. Otherwise, amethod of obtaining a diffraction grating member having a desired numberof layers (referred to as a “second method according to a related art”for convenience) has been adopted. According to the second method, ahologram recording film including a single layer is obtained by forminginterference fringes on the hologram recording film by performing anexposure attained by using a laser light beam, and fixing. After that,the above-described hologram recording film and a hologram recordingfilm material are bonded together, and the interference fringes areformed by subjecting the bonded hologram recording film material to anexposure and fixing so that a hologram recording film including twolayers is obtained. The above-described procedures are repeatedlyperformed so that the above-described diffraction grating member isobtained.

Since the above-described first and second methods are attained byperforming a large number of steps, yields are reduced and theproductivity is low. According to the second method, the hologramrecording film material is repeatedly subjected to the exposure and thefixing in sequence. However, when the hologram recording film materialis exposed, undesired interference fringes are formed on the hologramrecording film material due to interference fringes formed on thehologram recording film that had already been formed as an underlayer.Further, the above-described second method has the problem of mixing ofair bubbles or the like into the hologram recording film due to themanufacturing steps when the hologram recording film and the hologramrecording film material are bonded together.

Further, if a light source includes a light emitting diode (LED), forexample, the brightness of a light beam emitted from the seconddiffraction grating member 140 is determined based on the product of thedistribution of light emission spectrums of the light source and theefficiency of diffraction attained by the diffraction grating member.Since the diffraction efficiency significantly depends on the wavelengthof a light beam which is made incident on the diffraction gratingmember, it has been wished that the diffraction wavelength band of thediffraction grating member should be increased so that the brightness ofan image generated through the image display device is increased.

Further, since incident angles at which the plurality of collimatedlight beams are made incident on the first diffraction grating member130 differ based on the emission positions of the collimated lightbeams, the emission positions being defined on the image forming device111, are emitted from the image forming device 111, the diffractionwavelengths satisfying the Bragg condition vary among various regions ofthe first diffraction grating member 130. As a result, the diffractionefficiency of a light beam which is diffracted and reflected in thevarious regions of the first diffraction grating member 130 is varied.According to the above-described configuration, if a light beam which ismade incident on the first diffraction grating member 130 has a fixedwavelength band, the wavelength of the light beam diffracted at themaximum efficiency is varied based on the emission position from whichthe light beam is emitted, where the emission position is defined on theimage forming device 111, and the hue of a pixel image led to the eyes60 is varied due to the positions of pixels provided in the imageforming device 111. Further, when a light beam which is made incident onthe first diffraction grating member 130 has a single wavelength and thediffraction efficiency is varied based on a position from which thelight beam is emitted, the position being defined on the image formingdevice 111, brightness variations occur.

Firstly, therefore, the present invention provides a hologram recordingfilm manufacturing method in an embodiment which allows formanufacturing a hologram recording film having multiple diffractiongrating layers having interference fringes with different slant angles(inclination angle) φ according to a simple method, a hologram recordingfilm obtained through the above-described manufacturing method, and animage display apparatus including the hologram recording film.

Secondly, the present application provides a hologram recording filmmanufacturing method in an embodiment which allows for manufacturing ahologram recording film provided with regions having interferencefringes with different slant angles (inclination angles) φ so as toreduce color variations and/or brightness variations occurring due tothe incident angle of an incident collimated light beam according to asimple method.

Accordingly, a hologram recording film manufacturing method according toa first mode in an embodiment, which is attained to manufacture thehologram recording film having the multiple diffraction grating layershaving the interference fringes with the different slant angles(inclination angle) φ, includes the steps of (A) obtaining a laminatedstructure by alternately laminating M (where M≧2) photosensitivematerial precursor layers including a photosensitive material and atleast one (M−1) resin layer on one another, (B) obtaining Mphotosensitive material layers, where at least two interference fringeswith a desired pitch and a desired slant angle are formed on each of theM photosensitive material layers, from the M photosensitive materialprecursor layers by irradiating the laminated structure with a referencelaser light beam and an object laser light beam, and (C) making theslant angles of the M photosensitive material layers different from eachother while retaining a value of the pitch, the pitch being defined on aface of the photosensitive material layer, by irradiating the laminatedstructure with an energy ray from the laminated structure's one faceside, and heating the laminated structure subsequently.

A hologram recording film according to an embodiment, which is attainedto manufacture the hologram recording film having the multiplediffraction grating layers having the interference fringes with thedifferent slant angles (inclination angle) φ, includes a laminatedstructure including M (where M≧2) photosensitive material layersincluding a photosensitive material, where at least two interferencefringes with a desired pitch and a desired slant angle are formed oneach of the M photosensitive material layers, and at least one (M−1)resin layer that are alternately laminated on one another, whereinvalues of the pitches defined on faces of the M photosensitive materiallayers are identical to each other and the slant angles defined on thefaces of the M photosensitive material layers are different from eachother.

An image display apparatus according to the first mode in an embodiment,which is attained to manufacture the hologram recording film having themultiple diffraction grating layers having the interference fringes withthe different slant angles (inclination angle) φ, includes (A) an imageforming device having a plurality of pixels arranged in atwo-dimensional matrix form, (B) a collimating optical system configuredto make a light beam emitted from each of the pixels into a collimatedlight beam, and (C) an optical device onto which the collimated lightbeam is made incident, in which the collimated light beam is guided, andfrom which the collimated light beam is emitted. Further, an imagedisplay apparatus according to the first mode, which is attained tomanufacture the hologram recording film provided with the regions havingthe interference fringes with the different slant angles (inclinationangles) φ so as to reduce the color variations and/or the brightnessvariations occurring due to the incident angle of the incidentcollimated light beam according to the simple method, includes (A) alight source, (B) a collimating optical system making a light beamemitted from the light source into a collimated light beam, (C) ascanning means configured to scan the collimated light beam emitted fromthe collimating optical system, (D) a relay optical system configured torelay the collimated light beam scanned through the scanning means, and(E) an optical device onto which the collimated light beam is madeincident, in which the collimated light beam is guided, and from whichthe collimated light beam is emitted through the relay optical system.Further, an image display apparatus according to the first mode and/orthe second mode includes (a) a light guide plate through which a lightbeam which is made incident on the light guide plate propagates throughtotal reflection, and from which the light beam is emitted, (b) a firstdiffraction grating member provided in the light guide plate, the firstdiffraction grating member being configured to diffract and reflect thelight beam which is made incident on the light guide plate so that thelight beam which is made incident on the light guide plate is totallyreflected inside the light guide plate, and (c) a second diffractiongrating member provided in the light guide plate, the second diffractiongrating member being configured to diffract and reflect the light beamwhich propagates through the light guide plate through the totalreflection, and emit the light beam from the light guide plate, whereineach of the first and second diffraction grating members includes ahologram recording film having a laminated structure including M (whereM≧2) photosensitive material layers including a photosensitive material,where at least two interference fringes with a desired pitch and adesired slant angle are formed on each of the M photosensitive materiallayers, and at least one (M−1) resin layer that are alternatelylaminated on one another, wherein values of the pitches defined on facesof the M photosensitive material layers are identical to each other andthe slant angles defined on the faces of the M photosensitive materiallayers are different from each other.

Further, a hologram recording film manufacturing method according to thesecond mode in an embodiment, which is attained to manufacture thehologram recording film provided with the regions having theinterference fringes with the different slant angles (inclinationangles) φ so as to reduce the color variations and/or the brightnessvariations occurring due to the incident angle of the incidentcollimated light beam according to the simple method, includes the stepsof (A) obtaining a photosensitive material layer on which at least twointerference fringes with a desired pitch and a desired slant angle areformed from a photosensitive material precursor layer including aphotosensitive material by irradiating the photosensitive materialprecursor layer with a reference laser light beam and an object laserlight beam, and (B) making the slant angles observed in regions of thephotosensitive material layer different from each other while retaininga value of the pitch, the pitch being defined on a face of thephotosensitive material layer, by irradiating the regions with energyrays with different energy amounts, and heating the photosensitivematerial layer.

According to the hologram recording film manufacturing method accordingto the first mode in an embodiment, the laminated structure isirradiated with the reference laser light beam and the object laserlight beam so that the interference fringes are recorded onto thephotosensitive material (photopolymer) included in the photosensitivematerial precursor layer based on the refractive index modulation. Then,the laminated structure is irradiated with the energy ray from thelaminated structure's one face side so that monomers included in thephotosensitive material, the monomers being left without beingpolymerized at the laser irradiation time, are polymerized and fixed.Next, the laminated structure is heated so that the refractive indexmodulation factor is amplified. Through the heating, the refractiveindex modulation factor is increased and the slant angle (inclinationangle) of the interference fringes is changed due to a thermal stress.Since only the slant angle is changed while the value Λ of a pitchobserved on the surface of the photosensitive material layer isretained, the reproduction center wavelength (diffraction centerwavelength) is shifted from state “a” to state “b” as shown in FIG. 6A.Thus, the laminated structure is irradiated with the energy ray from thelaminated structure's one face side, and is heated so that the slantangles of the M photosensitive material layers are made different fromeach other while the value Λ of the pitch observed on the surface of thephotosensitive material layer is retained. Consequently, the number ofthe steps is not increased and the productivity is high. Further, themanufacturing method reduces undesired interference fringes formed onthe hologram recording film. Still further, the manufacturing methodreduces the mixing of air bubbles or the like into the hologramrecording film during the manufacturing steps. Further, since themanufacturing method allows for easily manufacturing a multilayerlaminated structure, the diffractive wavelength band of the diffractiongrating layer can further be increased and the brightness of an imagegenerated through the image display apparatus can be increased withfacility. Further, if an interference fringes allowing the shift amountof the reproduction center wavelength of each of the photosensitivematerial layers is recorded in advance, it becomes possible toarbitrarily design a desired reproduction center wavelength (diffractioncenter wavelength) and the bandwidth thereof.

Further, the hologram recording film manufacturing method according tothe second mode in an embodiment allows for making the slant anglesobserved in the regions of the photosensitive material layer differentfrom each other while retaining the value Λ of the pitch, the pitchbeing defined on the face of the photosensitive material layer, byirradiating the regions with energy rays with different energy amounts,and heating the photosensitive material layer. Consequently, the numberof the steps is not increased and the productivity is high. Since themanufacturing method allows for making the slant angles observed in theregions of the photosensitive material layer different from each other,it becomes possible to reduce color variations and/or brightnessvariations caused by the incident angle of an incident collimated lightbeam.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic sectional view of a laminated structure or thelike, which illustrates a hologram recording film manufacturing methodaccording to a first embodiment;

FIG. 1B is a schematic sectional view of a laminated structure or thelike, which illustrates the hologram recording film manufacturing methodaccording to the first embodiment;

FIG. 1C is a schematic sectional view of a laminated structure or thelike, which illustrates the hologram recording film manufacturing methodaccording to the first embodiment;

FIG. 2A is a schematic sectional view of a laminated structure or thelike, which illustrates a hologram recording film manufacturing methodaccording to a second embodiment;

FIG. 2B is a schematic sectional view of a laminated structure or thelike, which illustrates the hologram recording film manufacturing methodaccording to the second embodiment;

FIG. 3 is the sequel of FIG. 2B, that is, a schematic sectional view ofa laminated structure or the like, which illustrates the hologramrecording film manufacturing method according to the second embodiment;

FIG. 4A is a schematic sectional view of a laminated structure or thelike, which illustrates a hologram recording film manufacturing methodaccording to a third embodiment;

FIG. 4B is a schematic sectional view of a laminated structure or thelike, which illustrates the hologram recording film manufacturing methodaccording to the third embodiment;

FIG. 5 is the sequel of FIG. 4B, that is, a schematic sectional view ofa laminated structure or the like, which illustrates the hologramrecording film manufacturing method according to the third embodiment;

FIG. 6A is a graph showing the state where a reproduction centerwavelength (diffraction center wavelength) is shifted from state “a” tostate “b” when a photosensitive material layer is irradiated with anenergy ray, and heated;

FIG. 6B is a graph showing the relationship between the energy rayirradiation amount and the amount of a change in a slant angle, thechange occurring after the photosensitive material layer is heated;

FIG. 7 is a graph showing changes in diffraction wavelength bands, wherethe change occur when the same photosensitive material layers includingtwo layers are irradiated with energy rays, and heated;

FIG. 8A is a graph showing the width of a red diffraction wavelengthband obtained through a photosensitive material layer which diffractsand reflects a red light beam according to the first embodiment;

FIG. 8B is a graph showing the width of the red diffraction wavelengthband obtained through the photosensitive material layer which diffractsand reflects a red light beam according to the second embodiment;

FIG. 9 is a conceptual illustration of an exposure system configured toirradiate a laminated structure with a reference laser light beam and anobject laser light beam;

FIGS. 10A and 10B are conceptual illustrations of an image displayapparatus according to a fifth embodiment;

FIG. 11 is a conceptual illustration showing the state where a pair ofthe image display apparatuses of the fifth embodiment is worn by anobserver;

FIG. 12 is a conceptual illustration of an image display apparatusaccording to a sixth embodiment;

FIG. 13 is a conceptual illustration of an exemplary modulation of animage forming device that can be appropriately used in the fifthembodiment;

FIG. 14 is a conceptual illustration of another exemplary modulation ofthe image forming device that can be appropriately used in the fifthembodiment;

FIG. 15 is a conceptual illustration of another exemplary modulation ofthe image forming device that can be appropriately used in the fifthembodiment;

FIG. 16 is a conceptual illustration of another exemplary modulation ofthe image forming device that can be appropriately used in the fifthembodiment; and

FIG. 17 is a conceptual illustration of another exemplary modulation ofthe image forming device that can be appropriately used in the fifthembodiment.

DETAILED DESCRIPTION

The present application will be described with reference to the attacheddrawings according to an embodiment. Prior to that, a hologram recordingfilm, a method of manufacturing same, and an image display apparatusaccording to an embodiment will be specifically described. Hereinafter,a photosensitive material precursor layer including a photosensitivematerial will often be referred to as a “first photosensitive materialprecursor layer” so as to discriminate between the above-describedphotosensitive material precursor layer and a second photosensitivematerial precursor layer. Further, a photosensitive material layer willoften be referred to as a “first photosensitive material layer” so as todiscriminate between the above-described photosensitive material layerand a second photosensitive material layer, and a photosensitivematerial included in the first photosensitive material precursor layerwill often be referred to as a “first photosensitive material”. Further,the term “photosensitive material precursor layers” may denote both thefirst and second photosensitive material precursor layers, and the term“photosensitive material layers” may denote both the first and secondphotosensitive material layers. Still further, the term “pitch” maydenote a pitch defined on the face of the photosensitive material layer,and a pitch defined on the face of the photosensitive material layer maybe referred to as a “face pitch”.

Each of a hologram recording film obtained through a hologram recordingfilm manufacturing method according to a first mode in an embodiment, ahologram recording film according to an embodiment, and a hologramrecording film used for an image display apparatus according to thefirst mode and/or a second mode includes a laminated structure includingM photosensitive material layers and at least one M−1 resin layer thatare alternately laminated on one another. The above-described laminatedstructure includes a laminated structure including M photosensitivematerial layers and M resin layers that are alternately laminated on oneanother, and that including M photosensitive material layers and M+1resin layers that are alternately laminated on one another.

When using the hologram recording film manufacturing method according tothe first mode (hereinafter often abbreviated as a “manufacturing methodaccording to the first mode”), a method of forming dry film-likephotosensitive material precursor layers and laminating the dryfilm-like photosensitive material precursor layers on one another and/ora method of coating a supporting member including glass, a plastic, etc.with photosensitive materials in sequence in a desired order can be usedas a method of forming the laminated structure. A coating methodaccording to a related art may be used as the method of coating thephotosensitive material, where the coating method according to therelated art includes the die coating method, the gravure coating method,the roll coating method, the blade coating method, the curtain coatingmethod, the dip coating method, the spin coating method, a printingmethod, etc. Further, not only a single layer coating method but also amethod of coating a plurality of layers at the same time may be used,where the latter includes a multilayer slide coating method or the like.A protective layer (spacer layer) may be provided between thephotosensitive material precursor layers by using a coating means and/ora laminating method according to a related art, as appropriate. Anadhesive layer or the like may further be provided between thephotosensitive material precursor layer and the protective layer.Further, when placing the dry film-like photosensitive materialprecursor layer that had already been formed on the supporting memberfor use, the photosensitive material precursor layer may be placed onthe supporting member after the adhesive layer is provided on thesupporting member on which the photosensitive material precursor layeris placed.

When the photosensitive material precursor layer is protected by theprotective layer and the resin layer includes the second photosensitivematerial precursor layer including the second photosensitive material, alaminated structure having the following structure is obtained. Namely,the laminated structure includes the first first photosensitive materialprecursor layer/the protective layer/the first second photosensitivematerial precursor layer/the protective layer/the second firstphotosensitive material precursor layer/the protective layer/the secondsecond photosensitive material precursor layer/the third firstphotosensitive material precursor layer/the protective layer, and soforth when the first photosensitive material precursor layers and theresin layers are laminated on one another. Otherwise, when the resinlayer includes a film which absorbs part of an energy ray, a laminatedstructure having the following structure is obtained. Namely, thelaminated structure includes the first first photosensitive materialprecursor layer/the protective layer/the resin layer/the second firstphotosensitive material precursor layer/the protective layer/the resinlayer/the third first photosensitive material precursor layer/theprotective layer, and so forth. The lamination of the firstphotosensitive material precursor layers and the resin layers may beperformed according to a method appropriate for the above-describedmaterials.

Further, when performing the manufacturing method according to the firstmode and a hologram recording film manufacturing method according to thesecond mode in an embodiment, a laminated structure is irradiated with areference laser light beam and an object laser light beam so thatinterference fringes with desired surface pitches and slant angles areformed. The above-described methods may be a method according to arelated art. More specifically, for example, the laminated structureand/or the photosensitive material precursor layers may be irradiatedwith the object laser light beam from a first predetermined direction onone side at the same time as when the laminated structure and/or thephotosensitive material precursor layer is irradiated with the referencelaser light beam from the second predetermined direction on the otherside so that interference fringes formed through the object laser lightbeam and the reference laser light beam are recorded in the laminatedstructure and/or the photosensitive material precursor layers. The firstand second predetermined directions, and the wavelengths of the objectlaser light beam and the reference laser light beam should beappropriately selected so as to obtain the desired surface pitches andslant angles (inclination angles) of the interference fringes of thelaminated structure and/or the photosensitive material precursor layers.Here, the slant angle of the interference fringe denotes an angle whichthe surface of the hologram recording film forms with the interferencefringe.

The energy ray irradiation may be performed according to an appropriatemethod in accordance with an energy ray irradiation device (e.g., anultraviolet lamp) for use. Heating may also be performed according to anappropriate method, such as using a heating lamp, a hot plate, a heatingoven, etc. The heating temperature and the heating time may beappropriately determined based on materials included in thephotosensitive material layers. Usually, as the amount of energy givento the photosensitive material layers through the energy ray irradiationis increased, the amount of changes in the slant angles, the changesbeing observed after the heating, is decreased as shown in FIG. 6B.

Specifically, when the hologram recording film manufacturing methodaccording to the first mode and/or the second mode is performed, anultraviolet ray may be used as the energy ray. Otherwise, an electronbeam may be used. The wavelength, irradiation energy, irradiation time,and so forth of the ultraviolet ray for use may be appropriatelydetermined based on the characteristics of the photosensitive material.

When the hologram recording film manufacturing method of the first mode,the method having the above-described configurations, and/or a hologramrecording film according to an embodiment is used, the reproductioncenter wavelength of M first photosensitive material layers (the firstdiffraction grating layers) is changed based on the value of M (forexample, the reproduction center wavelength is monotonously changed).Namely, when the energy ray irradiation amount is made constant, thedifference between a reproduction center wavelength obtained before theenergy ray irradiation is performed and that obtained after the energyray irradiation is performed is increased as the value of M isincreased. Further, when the energy ray irradiation amount is changed,it may be arranged that the difference between the reproduction centerwavelength obtained before the energy ray irradiation is performed andthat obtained after the energy ray irradiation is performed is decreasedas the energy ray irradiation amount is increased.

When the hologram recording film manufacturing method according to thefirst mode, the method having the above-described configuration andform, is used, the resin layer includes the second photosensitivematerial precursor layer including a second photosensitive material,and, at the above-described step (B), the laminated structure isirradiated with the reference laser light beam and the object laserlight beam so that the M first photosensitive material layers on whichthe interference fringes with the desired pitches (surface pitches) andslant angles are formed are obtained from M first photosensitivematerial precursor layers. At the same time, at least one M−1 secondphotosensitive material layer on which second interference fringes withdesired pitches (surface pitches) and slant angles are formed areobtained from at least one M−1 second photosensitive material precursorlayer. The above-described manufacturing method will be referred to as a“first configuration manufacturing method” for convenience. If the valueof M−1 is two or more, the laminated structure is irradiated with anenergy ray from the laminated structure's first first photosensitivematerial layer side, and heated at the above-described step (C) so thatthe slant angles of the M first photosensitive material layers (thefirst diffraction grating layers) are made different from each other andthose of the M−1 second photosensitive material layers (the seconddiffraction grating layers) are made different from one another whileretaining the value A of the surface pitch. Further, the reproductioncenter wavelength of the M−1 second photosensitive material layers (thesecond diffraction grating layers) may be changed based on the value ofM (changed monotonously, for example).

According to the first configuration manufacturing method, thephotosensitive characteristic-for-an energy ray of the firstphotosensitive material layers may be different from that of the secondphotosensitive material layers. Otherwise, the photosensitivecharacteristics-for-the reference laser light beam and the object laserlight beam of the first photosensitive material precursor layer may bedifferent from those of the second photosensitive material layers. Inthat case, the first photosensitive material precursor layers should beirradiated with the first reference laser light beam and the firstobject laser light beam, and the second photosensitive materialprecursor layers should be irradiated with the second reference laserlight beam and the second object laser light beam, at theabove-described step (B). Further, the laser light beam irradiation forthe first photosensitive material precursor layers and that for thesecond photosensitive material precursor layers may be performed at thesame time or separately.

According to the first configuration manufacturing method, thephotosensitive characteristic-for-the energy ray of the firstphotosensitive material layers may be different from that of the secondphotosensitive material layers. Consequently, it becomes possible tomake the amount of energy with which the m-th (where the equation m=1,2, . . . , M holds) first photosensitive material layer is irradiateddifferent from that of energy with which the m′-th (where the equationm′=1, 2, . . . , M−1 holds) second photosensitive material layer isirradiated. As a result, the slant angles of the M first photosensitivematerial layers can be made different from each other and those of theM−1 second photosensitive material layers can be made different fromeach other. Further, by making the photosensitivecharacteristics-for-the reference laser light beam and the object laserlight beam of the first photosensitive material precursor layerdifferent from those of the second photosensitive material layers, theslant angles of the M first photosensitive material layers can be madedifferent from each other and those of the M−1 second photosensitivematerial layers can be made different from each other. Further, byirradiating the first photosensitive material precursor layers with thefirst reference laser light beam and the first object laser light beamand irradiating the second photosensitive material precursor layers withthe second reference laser light beam and the second object laser lightbeam, the pitches (surface pitches) and the slant angles of theinterference fringes formed on the first photosensitive materialprecursor layers can be made different from those of the interferencefringes formed on the second photosensitive material precursor layers.

Although the main compositions of the first and second photosensitivematerials are identical to each other, the energy ray transmittanceand/or the transmitted energy ray amount of the first photosensitivematerial may be different from that of the second photosensitivematerial. Otherwise, the main compositions of the first and secondphotosensitive materials may be made different from each other so thatthe energy ray transmittance and/or the transmitted energy ray amount ofthe first photosensitive material becomes different from that of thesecond photosensitive material. In the case where the energy raytransmittance and/or the transmitted energy ray amount of the firstphotosensitive material is different from that of the secondphotosensitive material even though the main compositions of the firstand second photosensitive materials are identical to each other, theamount of an energy ray absorbent (e.g., an ultraviolet absorbent)included in the first photosensitive material is different from thatincluded in the second photosensitive material, for example. Otherwise,the amount of a reaction initiator (e.g., an ultraviolet reactioninitiator), which is determined based on the energy rays, included inthe first photosensitive material is different from that included in thesecond photosensitive material, for example. Namely, the chemicalreaction for the energy rays, which occurs in the first photosensitivematerial, becomes different from that occurring in the secondphotosensitive material, for example. If the main compositions of thefirst photosensitive materials included in the individual M firstphotosensitive material layers are identical to each other, the energyray transmittances and/or the transmitted energy ray amounts of theindividual first photosensitive materials may be slightly different fromone another. Likewise, if the main compositions of the secondphotosensitive materials included in the individual M−1 secondphotosensitive material layers are identical to each other, the energyray transmittances and/or the transmitted energy ray amounts of theindividual second photosensitive materials may be slightly differentfrom each other.

When the hologram recording film manufacturing method according to thefirst mode, the method having the above-described configuration andform, is used, the resin layer may include a film absorbing part of theenergy ray. The above-described manufacturing method will be referred toas a “second configuration manufacturing method” for convenience. Here,the resin layer may have an absorbing characteristic so that the resinlayer absorbs 5% or more of ultraviolet radiation having a wavelength of400 nm or less. More specifically, a film including an acrylic-basedresin, an acrylic acid ester-based resin, a methacrylic acid resin, anepoxy-based resin, a urethane-based resin, a polyvinyl ether resin, apolycarbonate resin, a polyamide resin, a polyvinyl acetate, a vinylchloride-based resin, a urea-based resin, a styrene-based resin, abutadiene-based resin, a natural rubber-based resin, a polyvinylcarbazole, a polyethylene glycol, a phenol-based resin may beexemplarily used as a film absorbing part of an energy ray. Further,each of the above-described resins may include a material which absorbsan energy ray (e.g., an ultraviolet absorbent) as appropriate. Amaterial according to a related art may be used as the above-describedmaterial. Each of the above-described films may be formed according toan application method, or a film that had already been formed may beplaced.

In the case where a hologram recording film according to an embodiment,and an image forming device according to the first mode and/or thesecond mode are used, the resin layer may include the M−1 secondphotosensitive material layers (the second diffraction grating layers)including the second photosensitive material, where interference fringeshaving desired pitches (surface pitches) and slant angles are formed onthe M−1 second photosensitive material layers. The above-describedhologram recording film will be referred to as a “first configurationhologram recording film” for convenience. When the value of M−1 is twoor more, the surface pitches of the individual M−1 second photosensitivematerial layers are identical to one another and the slant angles of theindividual M−1 second photosensitive material layers are different fromone another.

In another case, when a hologram recording film according to anembodiment, and the image display apparatus according to the first modeand/or the second mode are used, the resin layer may include a filmabsorbing part of an energy ray. Further, the above-described hologramrecording film will be referred to as a “second configuration hologramrecording film” for convenience. Details of the resin layer are the sameas those of the above-described resin layer.

When the hologram recording film manufacturing method according to thesecond mode, the method having the above-described form, is used,individual regions of the photosensitive material layer are irradiatedwith energy rays with different energy amounts, where the energy amountmay be changed seamlessly or in stages. Further, the reproduction centerwavelengths of the individual regions of the photosensitive materiallayer (diffraction grating layer) may be different from one another.Still further, as the irradiation amount of the energy ray is decreased,the reproduction center wavelength approaches the long wavelength side.Namely, as the irradiation amount of the energy ray is decreased, thedifference between the reproduction center wavelength obtained beforethe energy ray irradiation is performed and that obtained after theenergy ray irradiation is performed may be increased.

If a photopolymer material included in the photosensitive materialprecursor layer may be any photopolymer material including, at least, aphotopolymerizable compound, a binder resin, and a photopolymerizationinitiator. The photopolymerizable compound may be a photopolymerizablecompound according to a related art, which includes an acrylic-basedmonomer, a methacrylic-based monomer, a styrene-based monomer, abutadiene-based monomer, a vinyl-based monomer, an epoxy-based monomer,and so forth. Each of the above-described monomers may be a copolymer,and a monofunctional material and/or a polyfunctional material. Theabove-described monomers may be used singly or in combination. Further,any binder resin according to a related art may be used as theabove-described binder resin. More specifically, a celluloseacetate-based resin, an acrylic-based resin, an acrylic acid ester-basedresin, a methacrylic acid resin, an epoxy-based resin, a urethane-basedresin, a polypropylene resin, a polyvinyl ether resin, a polycarbonateresin, a polyamide resin, a polyvinyl acetate, a vinyl chloride-basedresin, a urea-based resin, a styrene-based resin, a butadiene-basedresin, a natural rubber-based resin, a polyvinyl carbazole, apolyethylene glycol, a phenol-based resin, a copolymer including theabove-described resins, gelatin, and so forth may be used. The binderresins may also be used singly or in combination. Anyphotopolymerization initiator according to a related art may be used asthe above-described photopolymerization initiator. Thephotopolymerization initiators may be used singly or in combination.Further, the photopolymerization initiator may be used in combinationwith at least one photosensitizer pigment. A plasticizer, a chaintransfer agent, and other additives may be added to the photosensitivematerial precursor layer, as appropriate. The protective layer mayinclude any transparent material. The protective layer may be formedthrough coating and/or a material made into a film may be laminated ontothe photosensitive material precursor layer. The material included inthe protective layer may be, for example, a polyvinyl alcohol (PVA)resin, the acrylic resin, a polyurethane resin, a polyethyleneterephthalate (PET) resin, a cellulose triacetate (TAC) resin, apolymethyl methacrylate (PMMA) resin, the polypropylene resin, thepolycarbonate resin, and a polyvinyl chloride resin.

An image forming device provided in the image display apparatusaccording to the first mode may be, for example, an image forming deviceincluding a reflection type spatial light modulation device and a lightsource, an image forming device including a transmission type spatiallight modulation device and a light source, and an image forming deviceprovided with a light emitting element including an organicelectroluminescent (EL) element, an inorganic EL element, a lightemitting diode (LED), and so forth. Of the above-described image formingdevices, however, the image forming device including the reflection typespatial light modulation device and the light source should be used.Here, the spatial light modulation device may include a transmissiontype and/or reflection type liquid crystal display apparatus including alight valve such as a liquid crystal on silicon (LCOS), and a digitalmicromirror device (DMD), and the light source may include, for example,the light emitting element. Further, the reflection-type spatial lightmodulation device may include a liquid crystal display apparatus and apolarization beam splitter that reflects part of light emitted from thelight source, leads the light to the liquid crystal display apparatus,makes part of the light reflected by the liquid crystal displayapparatus pass, and leads the light to a collimating optical system. Thelight emitting element included in the light source may be a red lightemitting element, a green light emitting element, a blue light emittingelement, and a white light emitting element. Further, a semiconductorlaser element and/or an LED can be exemplified as the light emittingelement. The number of pixels may be determined based on appropriatespecifications of the image display apparatus. More specifically, thepixel number may be 320×240, 432×240, 640×480, 1024×768 and 1920×1080.

An image forming device provided in the image display apparatusaccording to the second mode may include a light emitting elementfunctioning as a light source. More specifically, the light emittingelement may include the red light emitting element, the green lightemitting element, the blue light emitting element, and the white lightemitting element. Further, a semiconductor laser element and/or an LEDcan be exemplified as the light emitting element. The number of pixels(virtual pixels) provided in the above-described image display apparatusmay be determined based on appropriate specifications of the imagedisplay apparatus. More specifically, the number of the pixels (virtualpixels) may be 320×240, 432×240, 640×480, 1024×768 and 1920×1080.Further, when the light source includes the red light emitting element,the green light emitting element, and the blue light emitting element,color synthesis may be performed through the use of a cross prism. As ascanning unit, a micro electro mechanical system (MEMS) such as a DMDand/or a galvanometer mirror, which performs horizontal scanning andvertical scanning for a light beam emitted from the light source may beused. A relay optical system may include a relay optical systemaccording to a related art.

In addition to a combination of the image forming device including thelight emitting elements and the light valve and/or a backlight whichentirely emits white light as the light source and a liquid crystaldisplay apparatus including red light emitting pixels, green lightemitting pixels, and blue light emitting pixels, the followingconfigurations may be exemplified.

[Image Forming Device—A]

An Image Forming Device—A Includes:

(α) a first image forming device including a first light emitting panelprovided with first light emitting elements emitting blue light beams,where the first light emitting elements are arranged in atwo-dimensional matrix form,

(β) a second image forming device including a second light emittingpanel provided with second light emitting elements emitting green lightbeams, where the second light emitting elements are arranged in thetwo-dimensional matrix form,

(γ) a third image forming device including a third light emitting panelprovided with third light emitting elements emitting red light beams,where the third light emitting elements are arranged in thetwo-dimensional matrix form, and

(δ) a unit provided to bring together the light beams that are emittedfrom the first, second, and third image forming devices into a singleoptical path (e.g., a dichroic prism as is the case with the followingdescriptions),

and controls the light emission/non-light emission state of each of thefirst, second, and third light emitting elements.

[Image Forming Device—B]

An Image Forming Device—B Includes:

(α) a first image forming device including a first light passage controldevice provided to control the first light emitting element emitting ablue light beam and the passage and/or the non-passage of the light beamemitted from the first light emitting element, where the first lightpassage control device is a type of light valve, and includes a liquidcrystal display apparatus, a DMD, a liquid crystal on silicon (LCOS),and so forth, as is the case with the following descriptions,

(β) a second image forming device including a second light passagecontrol device (light valve) provided to control the second lightemitting element emitting a green light beam and the passage and/or thenon-passage of the light beam emitted from the second light emittingelement,

(γ) a third image forming device including a third light passage controldevice (light valve) provided to control the third light emittingelement emitting a red light beam and the passage and/or the non-passageof the light beam emitted from the third light emitting element, and

(δ) a unit provided to bring together the light beams passing throughthe first, second, and third light passage control devices into a singleoptical path,

and displays an image by controlling the passage and/or the non passageof the light beams emitted from the above-described light emittingelements through the light passage control devices. A light guidemember, a microlens array, a mirror and/or a reflector, a condensinglens may be exemplified as a unit (light guide member) provided to leadthe light beams emitted from the first, second, and third light emittingelements to the light passage control devices.

[Image Forming Device—C]

An Image Forming Device—C Includes:

(α) a first image forming device including a first light emitting panelprovided with first light emitting elements emitting blue light beams,where the first light emitting elements are arranged in atwo-dimensional matrix form, and a blue light passage control device(light valve) provided to control the passage and/or the non-passage ofthe light beam emitted from the first light emitting panel,

(β) a second image forming device including a second light emittingpanel provided with second light emitting elements emitting green lightbeams, where the second light emitting elements are arranged in atwo-dimensional matrix form, and a green light passage control device(light valve) provided to control the passage and/or the non-passage ofthe light beam emitted from the second light emitting panel,

(γ) a third image forming device including a third light emitting panelprovided with third light emitting elements emitting red light beams,where the third light emitting elements are arranged in atwo-dimensional matrix form, and a red light passage control device(light valve) provided to control the passage and/or the non-passage ofthe light beam emitted from the third light emitting panel, and

(δ) a unit provided to bring together the light beams passing throughthe blue light passage control device, the green light passage controldevice, and the red light passage control device into a single opticalpath,

and displays an image by controlling the passage and/or the non passageof the light beams emitted from the first, second, and third lightemitting panels through the light passage control devices (lightvalves).

[Image Forming Device—D]

An image forming device D is configured to display a color image underthe field sequential system, and includes

(α) a first image forming device including at least one first lightemitting element emitting a blue light beam,

(β) a second image forming device including at least one second lightemitting element emitting a green light beam, and

(γ) a third image forming device including at least one third lightemitting element emitting a red light beam, and

(δ) a unit provided to bring together the light beams emitted from thefirst, second, and third image forming devices into a single opticalpath, and

(∈) a light passage control device (light valve) configured to controlthe passage and/or the non-passage of the light beams emitted from theabove-described unit,

wherein the image forming device displays an image by controlling thepassage and/or the non-passage of the light beams emitted from theabove-described light emitting elements through the light passagecontrol device.

[Image Forming Device—E]

An image forming device E is also configured to display a color imageunder the field sequential system, and includes

(α) the first image forming device including the first light emittingpanel provided with the first light emitting elements emitting bluelight beams, where the first light emitting elements are arranged in thetwo-dimensional matrix form,

(β) the second image forming device including the second light emittingpanel provided with the second light emitting elements emitting greenlight beams, where the second light emitting elements are arranged inthe two-dimensional matrix form,

(γ) the third image forming device including the third light emittingpanel provided with the third light emitting elements emitting red lightbeams, where the third light emitting elements are arranged in thetwo-dimensional matrix form, and

(δ) the unit provided to bring together the light beams that are emittedfrom the individual first, second, and third image forming devices intoa single optical path, and

(∈) the light passage control device (light valve) configured to controlthe passage and/or the non-passage of the light beams emitted from theabove-described unit,

wherein the image forming device—E displays an image by controlling thepassage and/or the non-passage of the light beams emitted from theabove-described light emitting panels through the light passage controldevice.

[Image Forming Device—F]

An image forming device F is a passive matrix-type and/or activematrix-type image forming device displaying a color image by controllingthe light emission state and/or the non-light emission state of each ofthe first, second, and third light emitting elements.

[Image Forming Device—G]

An image forming device—G is an image forming apparatus displaying acolor image under the field sequential system. The image formingdevice—G includes a light passage control device (light valve)configured to control the passage and/or the non-passage of light beamsemitted from light emitting element units that are arranged in atwo-dimensional matrix form, performs time-division control for thelight emission state and/or the non-light emission state of each of thefirst, second, and third light emitting elements provided in the lightemitting element units, and controls the passage and/or the non-passageof light beams emitted from the first, second, and third light emittingelements through the light passage control device so that the colorimage is displayed.

According to the image display apparatus according to the first modeand/or the second mode, the light beams are made into collimated lightbeams and are made incident on a light guide plate. The reason why thelight beams are collimated is that light wavefront information obtainedwhen the above-described light beams are made incident on the lightguide plate should be stored after the light beams are emitted from thelight guide plate via first and second diffraction grating members. Morespecifically, for generating the collimated light beams, the imageforming device may be arranged, for example, at the place (position) ofa focal length defined in a collimating optical system. Here, thecollimating optical system has a function of converting informationabout the pixel position into angle information of an optical systemprovided in an optical device.

In the image display apparatus according to the first mode and/or thesecond mode, the light guide plate has two parallel faces (the first andsecond faces) extending in parallel with the axis line (Y-direction) ofthe light guide plate. Here, when the face of the light guide plate, onwhich the light beams are made incident, is determined to be the lightguide plate-incident face and the face of the light guide plate, fromwhich the light beams are emitted, is determined to be the light guideplate-emission face, the light guide plate-incident face and the lightguide plate-emission face may be defined on the first face. Otherwise,the light guide plate-incident face may be defined on the first face andthe light guide plate-emission face may be defined on the second face.

Materials included in the light guide plate may be glass such as opticalglass including silica glass, BK7, and so forth and/or a plasticmaterial including the PMMA, the polycarbonate resin, the acrylic-basedresin, an amorphous polypropylene-based resin, a styrene-based resinincluding an acrylonitrile styrene (AS) resin, and so forth. Withoutbeing limited to the flat shape, the light guide plate may have anyshape and be curved.

As the collimating optical system included in the image displayapparatus according to the first mode and/or the second mode, an opticalsystem using a convex lens, a concave lens, a free form surface prism,and a hologram lens singly or in combination may be exemplified, wherethe optical system has a positive optical power on the whole.

The use of the image display apparatus according to the first modeand/or the second mode allows for, for example, configuring a lightweight and small head mounted display (HMD), significantly reducing userdiscomfort caused by the HMD placed on the user's head, and reducing themanufacturing cost.

First Embodiment

A first embodiment relates to the hologram recording film manufacturingmethod according to the first mode. More specifically, the firstembodiment relates to the first configuration manufacturing method, anda hologram recording film according to an embodiment. More specifically,the first embodiment relates to the first configuration hologramrecording film.

As shown in a schematic sectional view of FIG. 1C, a hologram recordingfilm 30 according to the first embodiment includes a laminated structure33 having the M (where the expression M≧2 holds, and the equation M=2holds in the first embodiment) first photosensitive material layers (thefirst diffraction grating layers) 31A and 31B including the firstphotosensitive material, and at least one M−1 resin layer that arealternately laminated on one another, where interference fringes havingdesired surface pitches and slant angles are formed on the M firstphotosensitive material layers 31A and 31B. The values of the pitchesobserved on the faces (surface pitches) of the individual M firstphotosensitive material layers 31A and 31B are identical to each other,and the slant angles of the individual M first photosensitive materiallayers 31A and 31B are different from each other.

In each of FIGS. 1B and 1C, and/or FIGS. 2B, 3, 4B, and 5 that will bedescribed later, each of protective layers 14 is not diagonally shaded.Further, in each of FIGS. 1B and 1C, and/or FIGS. 2B, 3, 4B, and 5 thatwill be described later, each of the first photosensitive materiallayers 31A, 31B, and 31C, and second photosensitive material layers 32Aand 32B is diagonally shaded. The above-described shading schematicallyshows the interference fringes.

Here, in the first embodiment, the resin layer includes a secondphotosensitive material precursor layer 12A including the secondphotosensitive material. Further, the resin layer includes at least oneM−1 (specifically, M−1 denotes one in the first embodiment) secondphotosensitive material layer (the second diffraction grating layer) 32Aon which interference fringes with a desired surface pitch and a desiredslant angle are formed.

The values of the surface pitches, the slant angles, and thereproduction center wavelengths (λ) of the first first photosensitivematerial layer 31A, which denotes the first layer of the firstphotosensitive material layers (hereinafter the above-describeddesignation scheme is also applied to any other photosensitive materiallayer), the second first photosensitive material layer 32A, and thefirst second photosensitive material layer 31B are exemplarily shown inTable 1 as below. Here, in Table 1 and/or Tables 3 and 5 which will bedescribed later, the value shown before the sign “/” used for each ofthe slant angle values and the reproduction center wavelengths denotes avalue obtained after the photosensitive material layer is heated.Further, the value shown after the sign “/” is a value obtained beforethe photosensitive material layer is heated. Since the first firstphotosensitive material layer includes the same photosensitive materialas that of the second first photosensitive material layer, thediffraction wavelength bands thereof, which are observed before theabove-described photosensitive material layers are heated, are the sameas each other as shown in FIG. 7 (refer to peak “A” shown in FIG. 7).However, after being heated, the diffraction wavelength band of thefirst first photosensitive material layer is changed differently fromthat of the second first photosensitive material layer as indicated bypeaks “C” and “B” that are shown in FIG. 7.

TABLE 1 Surface Slant Reproduction Center Pitch Angle Wavelength (λ)First first photosensitive 0.4 μm 31.6°/29.5° 626 nm/596 nm materiallayer First second photosensitive 0.3 μm 32.2°/29.5° 455 nm/427 nmmaterial layer Second first photosensitive 0.4 μm 32.9°/29.5° 644 nm/596nm material layer

As described above, the surface pitches of the M first photosensitivematerial layers 31A and 31B are different from that of the M−1 secondphotosensitive material layer 32A. Further, each of the reproductioncenter wavelengths of the M first photosensitive material layers 31A and31B approaches the long wavelength side as the value M is increased.Namely, as the energy ray irradiation amount is decreased, thedifference between the reproduction center wavelength obtained beforethe energy ray irradiation is performed and that obtained after theenergy ray irradiation is performed is increased.

Hereinafter, the hologram recording film manufacturing method accordingto the first embodiment, more specifically, the first configurationmanufacturing method will be described. In the first embodiment, thephotosensitive characteristic-for-energy ray of the first photosensitivematerial layer is different from that of the second photosensitivematerial layer. More specifically, even though the first photosensitivematerial included in the first photosensitive material layer has thesame main composition as that of the second photosensitive materialincluded in the second photosensitive material layer, the transmittedenergy ray amount of the first photosensitive material is different fromthat of the second photosensitive material. More specifically, sinceeach of the photosensitive material layers absorbs an energy ray, thetransmitted energy ray amounts of the photosensitive material layers aredifferent from one another. Specifically, the energy ray may be anultraviolet ray having a wavelength of 365 nm. Further, thephotosensitive characteristics-for-reference laser light and objectlaser light of the first photosensitive material precursor layer aredifferent from those of the second photosensitive material precursorlayer.

[Step—100]

First, M (where the expression M≧2 holds, and the equation M=2 holds inthe first embodiment) first photosensitive material layers 11A and 11Bthat include the first photosensitive material and at least one M−1resin layer are alternately laminated on one another so that a laminatedstructure 13 is obtained (refer to FIG. 1A).

Specifically, a PVA (NH-18 manufactured by Nippon Synthetic ChemicalIndustry Co., Ltd) is applied onto a support film including a PET anddried so that the protective layer 14 having a thickness of 5 μm isprovided. Next, a photopolymer having a photosensitive characteristicfor green laser light (HRS 700×380 including a green pigment forexposure, which is manufactured by Du Pont Kabushiki Kaisha) is appliedonto the protective layer 14 so as to obtain the first photosensitivematerial precursor layers 11A and 11B with a thickness of 10 μm andcohesiveness. Similarly, a photopolymer having a photosensitivecharacteristic for blue laser light (HRS 700×380 including a bluepigment for exposure, which is manufactured by Du Pont Kabushiki Kaisha)is applied onto the protective layer 14 so as to obtain a secondphotosensitive material precursor layers 12A with a thickness of 10 μmand cohesiveness. The obtained first photosensitive material precursorlayer 11B is placed on a support member 15 including a glass plate andthe support film is removed. Then, the second photosensitive materialprecursor layer 12A is placed on the protective layer 14 provided on thefirst photosensitive material precursor layer 11B and the support filmis removed. After that, the first photosensitive material precursorlayer 11A is placed on the protective layer 14 provided on the secondphotosensitive material precursor layer 12A, and the support film isremoved. Thus, as shown in a schematic sectional view of FIG. 1A, thesecond first photosensitive material precursor layer 11B, the protectivelayer 14, the first second photosensitive material precursor layer 12A,the protective layer 14, the first first photosensitive materialprecursor layer 11A, and the protective layer 14 are laminated onto thesupport member 15 so as to obtain the laminated structure 13.

[Step—110]

Next, the laminated structure is irradiated with the reference laserlight beam and the object laser light beam so that the M firstphotosensitive material layers 21A and 21B on which interference fringeswith desired pitches (surface pitches) and slant angles are formed areobtained from the M first photosensitive material precursor layers 11Aand 11B. In addition to that, at least one M−1 second photosensitivematerial layer 22A on which second interference fringes with desiredpitches (surface pitches) and slant angles are formed are obtained fromthe M−1 second photosensitive material precursor layer 12A (refer toFIG. 1B).

Specifically, the first photosensitive material precursor layers 11A and11B are irradiated with the first reference laser light beam and thefirst object laser light beam, and the second photosensitive materialprecursor layer 12A is irradiated with the second reference laser lightbeam and the second object laser light beam. More specifically, thelaminated structure 13 is secured to a prism for exposure throughrefractive oil. Then, the first photosensitive material precursor layers11A and 11B are irradiated with the first reference light beam and thefirst object laser light beam that are emitted from a YAG laser (secondharmonic generation (SHG)) configured to emit a green light beam havinga wavelength of 532 nm. At the same time, the second photosensitivematerial precursor layer 12A is irradiated with the second referencelaser light beam and the second object laser light beam that are emittedfrom an argon (Ar) laser configured to emit a blue light beam having awavelength of 457 nm.

An exposure system schematically shown in FIG. 9 includes laser lightsources (a laser light source 41 including the YAG laser and a laserlight source 51 including the argon (Ar) laser), where each of the laserlight sources is configured to emit a laser light beam having apredetermined wavelength, and variable beam splitters 43 and 53 that arearranged on optical axes of the laser light beams emitted from theindividual laser light sources 41 and 51. The variable beam splitters 43and 53 are provided to separate the laser light beams that are emittedfrom the individual laser light sources 41 and 51 into the referencelaser light beams and the object laser light beams.

More specifically, the laser light beam emitted from the laser lightsource 41 is totally reflected by a total reflection mirror 42, and ismade incident on the variable beam splitter 43. Here, the laser lightbeam reflected by the variable beam splitter 43 becomes the referencelaser light beam, and the laser light beam which passes through thevariable beam splitter 43 becomes the object laser light beam. Further,the laser light beam emitted from the laser light source 51 is totallyreflected by a total reflection mirror 52, and is made incident on thevariable beam splitter 53. The laser light beam reflected by thevariable beam splitter 53 becomes the reference laser light beam, andthe laser light beam which passes through the variable beam splitter 53becomes the object laser light beam. Here, the reference laser lightbeams of the individual colors, which are separated through the variablebeam splitters 43 and 53 are subjected to color synthesis through adichroic mirror 48. The reference laser light beam subjected to thecolor synthesis is made incident on the laminated structure via a beamshaping optical system 50 provided for a reference laser light beam.Here, total reflection mirrors 47 and 49 are provided in the opticalpath of the above-described reference laser light beam so as to changethe travel direction of the reference laser light beam. On the otherhand, the object laser light beams of the individual colors, which areseparated through the variable beam splitters 43 and 53 are subjected tocolor synthesis through a dichroic mirror 44. The object laser lightbeams subjected to the color synthesis are made incident on thelaminated structure via a beam shaping optical system 46 provided forthe object laser light beams. Here, total reflection mirrors 45 and 54are provided in the optical path of the above-described reference laserlight beam so as to change the travel direction of the object laserlight beam. Consequently, the reference laser light beam and the objectlaser light beam interfere with each other inside the photosensitivematerial precursor layer included in the laminated structure, andinterference fringes caused by the reference laser light beam and theobject laser light beam interfering with each other are recorded in thephotosensitive material precursor layer as changes in the refractiveindex. In the above-described embodiment, multi-wavelength simultaneousexposure has been exemplarily described. Namely, the blue laser lightbeam and the green laser light beam are subjected to the color synthesisand the laminated structure is irradiated with the blue laser light beamand the green laser light beam at the same time so that the laminatedstructure is exposed. However, the laminated structure may be irradiatedwith the blue laser light beam and the green laser light beam separatelyand sequentially. Namely, the laminated structure may be subjected tomulti-wavelength sequential exposure. Since the above-describedconfiguration is also applied to the red laser light beam, thedescription thereof is omitted. Further, the laminated structure may beexposed to the three color laser light beams at the same time and insequence.

[Step—120]

After that, the laminated structure 23 is irradiated with an energy rayfrom the laminated structure 23's one face side, and heated.Consequently, the slant angles of the M first photosensitive materiallayers 31A and 31B become different from each other while the value Λ ofthe surface pitch is retained.

Specifically, the laminated structure 23 is irradiated with anultraviolet ray from the first first photosensitive material layer 21A'sside. The ultraviolet irradiation amount is determined to be 22 Joules.When the ultraviolet ray passes through the first photosensitivematerial layer 21A, the second photosensitive material layer 22A, andthe first photosensitive material layer 21B, about 50 percent of theenergy thereof is absorbed by each of the first photosensitive materiallayer 21A, the second photosensitive material layer 22A, and the firstphotosensitive material layer 21B. Consequently, the amounts ofultraviolet with which the photosensitive material layers 21A, 22A, and21B are irradiated are as shown in Table 2 that follows. After that, thelaminated structure 23 is heated to 100° C. for eighty minutes throughan oven. After that, the support member 15 is removed so that thehologram recording film 30 according to the first embodiment isobtained, where the hologram recording film 30 has the configurationshown in FIG. 1C.

TABLE 2 Ultraviolet irradiation amount (Joule) First firstphotosensitive material layer 21A 22 First second photosensitivematerial layer 22A 11 Second first photosensitive material layer 21B 5.5

The changes in the values of the reproduction center wavelengths, thechanges being observed before and after the laminated structure isheated, are as shown in Table 1. Further, as shown in FIG. 8A, the widthof a red diffractive wavelength band of which center is 635 nm isincreased to 38 nm. Here, before the laminated structure is heated, thewidth of the red diffractive wavelength band of which center is 596 nmis 11 nm.

Thus, according to the hologram recording film manufacturing method ofthe first embodiment, the laminated structure is irradiated with anenergy ray from the laminated structure's one face side, and heated.Consequently, the slant angles of the M first photosensitive materiallayers become different from each other while the value Λ of the surfacepitch is retained. Namely, the values of the pitches defined on thesurfaces of the M first photosensitive material layers are the same aseach other, and the slant angles observed on the surfaces of the M firstphotosensitive material layers are different from each other. Therefore,the number of the steps of manufacturing the hologram recording film isnot increased and the productivity is high. Further, the manufacturingmethod reduces undesired interference fringes formed on the hologramrecording film, which had occurred according to related arts. Stillfurther, the manufacturing method reduces the mixing of air bubbles orthe like into the hologram recording film during the manufacturingprocedures. Further, since the manufacturing method allows for easilymanufacturing a multilayer laminated structure, the diffractivewavelength band of the diffraction grating layer can further beincreased and the brightness of an image generated through the imagedisplay apparatus can be increased with facility.

Second Embodiment

A second embodiment is a modulation of the first embodiment. In thesecond embodiment, the equation M=3 holds. The first photosensitivematerial precursor layers 11A, 11B, and 11C, and the secondphotosensitive material precursor layers 12A and 12B that are used inthe second embodiment are the same as the first photosensitive materialprecursor layers 11A and 11B, and the second photosensitive materialprecursor layer 12A that are used in the first embodiment. However, theconditions for irradiating the laminated structure with the referencelaser light beam and the object laser light beam are slightly differentfrom those of the first embodiment.

The values of the surface pitches, the slant angles, and thereproduction center wavelengths (λ) of the first first photosensitivematerial layer 31A, the second first photosensitive material layer 31B,the third first photosensitive material layer 31C, the first secondphotosensitive material layer 32A, and the second second photosensitivematerial layer 32B that are obtained are exemplarily shown in Table 3that follows.

TABLE 3 Surface Slant Reproduction Center Pitch Angle Wavelength (λ)First first photosensitive 0.4 μm 30.3°/28.8° 607 nm/585 nm materiallayer First second photosensitive 0.3 μm 31.2°/29.3° 445 nm/425 nmmaterial layer Second first photosensitive 0.4 μm 31.5°/28.8° 625 nm/585nm material layer Second second photosensitive 0.3 μm 32.7°/29.3° 460nm/425 nm material layer Third first photosensitive 0.4 μm 32.4°/28.8°638 nm/585 nm material layer

Schematic sectional views of laminated structures or the like obtainedthrough the steps of manufacturing a hologram recording film 30A of thesecond embodiment are shown in FIGS. 2A, 2B, and 3. The schematicsectional view of FIG. 2A shows the laminated structure or the likeobtained through a step identical to [Step—100] shown in FIG. 1A of thefirst embodiment. The schematic sectional view of FIG. 2B shows thelaminated structure or the like obtained through a step identical to[Step—110] shown in FIG. 1B of the first embodiment. The schematicsectional view of FIG. 3 shows the laminated structure or the likeobtained through a step identical to [Step—120] shown in FIG. 1C of thefirst embodiment. The reference numerals 21A, 21B, and 21C denote thefirst photosensitive material layers obtained after the interferencefringes are formed and before being irradiated with energy rays. Thereference numerals 22A and 22B denote the second photosensitive materiallayers obtained after the interference fringes are formed and beforebeing irradiated with energy rays.

In the second embodiment, the surface pitches of the M−1 secondphotosensitive material layers 32A and 32B are the same as each otherwhile the slant angles of the M−1 second photosensitive material layers32A and 32B are different from each other. The reproduction centerwavelength of each of the M−1 second photosensitive material layers 32Aand 32B approaches the long-wavelength side as the value of M isincreased. Namely, the difference between the reproduction centerwavelength obtained before the energy ray irradiation is performed andthat obtained after the energy ray irradiation is performed is increasedas the energy ray irradiation amount is decreased.

The changes in the values of the reproduction center wavelengths, thechanges being observed before and after the laminated structure isheated, are as shown in Table 3. Further, as shown in FIG. 8B, the widthof a red diffractive wavelength band of which center is 630 nm isincreased to 51 nm. Here, before the laminated structure is heated, thewidth of a red diffractive wavelength band of which center is 585 nm is12 nm. Further, though not shown, the width of a blue diffractivewavelength band of which center is 453 nm is increased to 35 nm. Beforethe laminated structure is heated, the width of a blue diffractivewavelength band of which center is 425 nm is 8 nm.

The ultraviolet irradiation amount is determined to be 48 Joules. Whenthe ultraviolet ray passes through the photosensitive material layers,about 50 percent of the energy of the ultraviolet ray is absorbed by thephotosensitive material layers. Consequently, the amounts of ultravioletwith which the photosensitive material layers are irradiated are asshown in Table 4 that follows. Further, the laminated structure isheated to 100° C. for eighty minutes through an oven.

TABLE 4 Ultraviolet irradiation amount (Joule) First firstphotosensitive material layer 21A 48 First second photosensitivematerial layer 22A 24 Second first photosensitive material layer 21B 12Second second photosensitive material layer 22B 6 Third firstphotosensitive material layer 21C 3

Third Embodiment

A third embodiment, which is another modulation of the first embodiment,relates to the second configuration manufacturing method and a secondconfiguration hologram recording film 30B. In the third embodiment, eachof resin layers 16A and 16B includes a film absorbing part of an energyray. Specifically, each of the resin layers 16A and 16B includes a filmincluding an acrylic-based resin having a thickness of 5 μm. Theabove-described film absorbs 15 percent of an ultraviolet ray having awavelength of 365 nm. The index of the ultraviolet absorption iscalculated by measuring the ultraviolet intensity corresponding to thewavelength of 365 nm observed prior to and subsequent to the ultraviolettransmission through the use of Light Power meter Model C6080-03manufactured by Hamamatsu Photonics K.K. In the third embodiment, theequation M=3 holds. The first photosensitive material precursor layers11A, 11B, and 11C that are used in the third embodiment are the same asthe first photosensitive material precursor layers 11A and 11B that areused in the first embodiment. However, the conditions for irradiatingthe laminated structure with the reference laser light beam and theobject laser light beam are slightly different from those of the firstembodiment.

According to a manufacturing method of the third embodiment, thelaminated structure is irradiated with an energy ray from the laminatedstructure's first first photosensitive material layer side at theabove-described step (C).

The values of the surface pitches, the slant angles, and thereproduction center wavelengths (λ) of the first first photosensitivematerial layer 31A, the second first photosensitive material layer 31B,and the third first photosensitive material layer 31C that are obtainedare exemplarily shown in Table 5 that follows.

TABLE 5 Surface Slant Reproduction Center Pitch Angle Wavelength (λ)First first photosensitive 0.4 μm 30.3°/29.3° 607 nm/592 nm materiallayer Second first photosensitive 0.4 μm 31.2°/29.3° 621 nm/592 nmmaterial layer Third first photosensitive 0.4 μm 32.6°/29.3° 640 nm/592nm material layer

Schematic sectional views of laminated structures or the like obtainedthrough the steps of manufacturing the hologram recording film 30B ofthe third embodiment are shown in FIGS. 4A, 4B, and 5. The schematicsectional view of FIG. 4A shows the laminated structure or the likeobtained through a step identical to [Step—100] shown in FIG. 1Adescribed in the first embodiment. The schematic sectional view of FIG.4B shows the laminated structure or the like obtained through a stepidentical to [Step—110] shown in FIG. 1B described in the firstembodiment. The schematic sectional view of FIG. 5 shows the laminatedstructure or the like obtained through a step identical to [Step—120]shown in FIG. 1C described in the first embodiment. The referencenumerals 21A, 21B, and 21C denote the first photosensitive materiallayers obtained after the interference fringes are formed and beforebeing irradiated with energy rays.

The changes in the values of the reproduction center wavelengths, thechanges being observed before and after the laminated structure isheated, are as shown in Table 5. The width of a diffractive wavelengthband of which center is 622 nm is increased to 52 nm. Before thelaminated structure is heated, the width of a diffractive wavelengthband of which center is 592 nm is 10 nm.

The ultraviolet irradiation amount is determined to be 58 Joules. Whenthe ultraviolet ray passes through the photosensitive material layers,about 50 percent of the energy of the ultraviolet ray is absorbed by thephotosensitive material layers, and about 15 percent of the energy ofthe ultraviolet ray is absorbed by the resin layers. Consequently, theamounts of ultraviolet with which the photosensitive material layers areirradiated are as shown in Table 6 that follows. After that, thelaminated structure is heated to 100° C. for eighty minutes through anoven.

TABLE 6 Ultraviolet irradiation amount (Joule) First firstphotosensitive material layer 31A 58 Second first photosensitivematerial layer 31B 24.7 Third first photosensitive material layer 31C10.5

Fourth Embodiment

A fourth embodiment relates to the hologram recording film manufacturingmethod according to the second mode in an embodiment.

The hologram recording film manufacturing method includes:

(A) obtaining at least one photosensitive material layer on which atleast two interference fringes with a desired pitch (surface pitch) anda desired slant angle are formed from a first photosensitive materialprecursor layer including a photosensitive material by irradiating thefirst photosensitive material precursor layer with a reference laserlight beam and an object laser light beam; and

(B) irradiating regions of the photosensitive material layer with energyrays with different energy amounts, and heating the photosensitivematerial layer so as to make slant angles of the regions of thephotosensitive material layer (diffraction grating layer) different fromeach other while retaining the value Λ of the pitch (surface pitch)defined on the surface of the photosensitive material layer.

Step (A) may be substantially equal to [Step—110] described in the firstembodiment, and step (B) may be substantially equal to [Step—120]described in the first embodiment except that the regions of thephotosensitive material layer are irradiated with energy rays withdifferent energy amounts. For irradiating the regions of thephotosensitive material layer with the energy rays with the differentenergy amounts, the integrals of the amounts of energy with which theregions of the photosensitive material layer are irradiated may be madedifferent from each other and/or the energy ray irradiation amount perunit area may be varied among the regions. The energy amount may bechanged seamlessly and/or in stages based on appropriate specificationsof the image display apparatus.

In the fourth embodiment, the reproduction center wavelength observed inthe obtained photosensitive material layer (diffraction grating layer)is varied among the regions of the photosensitive material layer(diffraction grating layer. The reproduction center wavelengthapproaches the long-wavelength side as the amount of the energy rayirradiation is decreased. Namely, the difference between thereproduction center wavelength obtained before the energy rayirradiation is performed and that obtained after the energy rayirradiation is performed is increased as the energy ray irradiationamount is decreased. Thus, according to the hologram recording film ofthe fourth embodiment, the regions of the photosensitive material layerare irradiated with energy rays with different energy amounts, and thephotosensitive material layer is heated so that slant angles of theregions of the photosensitive material layer (diffraction grating layer)are made different from each other while retaining the value Λ of thesurface pitch. Consequently, the number of the steps is not increasedand the productivity is high. The hologram recording film obtainedthrough the fourth embodiment can be used for the first diffractiongrating member and/or the second diffraction grating member used in theoptical device disclosed in Japanese Unexamined Patent ApplicationPublication No. 2007-094175, for example.

Fifth Embodiment

A fifth embodiment relates to an image display apparatus 100 accordingto a first mode in an embodiment. As shown in a conceptual illustrationof FIG. 10A, the image display apparatus 100 includes:

(A) an image forming device 111 including a plurality of pixels that arearranged in a two-dimensional matrix form,

(B) a collimating optical system 112 configured to make a light beamemitted from each of the pixels of the image forming device 111 into acollimated light beam, and

(C) an optical device 120 onto which the above-described collimatedlight beam is made incident, in which the collimated light beam isguided, and from which the collimated light beam is emitted.

In the first embodiment, the optical device 120 includes:

(a) a light guide plate 121 through which a light beam which is madeincident on the light guide plate 121 propagates and from which thelight beam is emitted,

(b) a first diffraction grating member 130 provided in the light guideplate 121, the first diffraction grating member 130 being configured todiffract and reflect the light beam which is made incident on the lightguide plate 121 so that the above-described light beam is totallyreflected inside the light guide plate 121, and

(c) a second diffraction grating member 140 provided in the light guideplate 121, the second diffraction grating member 130 being configured todiffract and reflect the light beam propagating through the light guideplate 121 through the total reflection and emit the above-describedlight beam from the light guide plate 121,

wherein each of the first and second diffraction grating members 130 and140 includes the hologram recording film described in any one of thefirst to third embodiments and a reflection-type volume hologramdiffraction grating. Here, the term “reflection-type volume hologramdiffraction grating” denotes a hologram diffraction grating configuredto diffract and reflect a plus primary diffraction light beam alone.

Namely, the hologram recording film includes the laminated structurehaving the M (where the expression M≧2 holds) first photosensitivematerial layers and the M−1 resin layer that are alternately laminatedon one another, where interference fringes having desired surfacepitches and slant angles are formed on the M first photosensitivematerial layers including the photosensitive material. The surfacepitches of the M first photosensitive material layers are identical toeach other, and the slant angles of the M first photosensitive materiallayers are different from each other.

The first diffraction grating member 130 is provided (adhered) onto asecond face 123 of the light guide plate 121, and diffracts and reflectsthe above-described collimated light beam which is made incident from afirst face 122 of the light guide plate 121 onto the light guide plate121 so that the collimated light beam is totally reflected inside thelight guide plate 121. Further, the second diffraction grating member140 is provided (adhered) onto the second face 123, diffracts andreflects the collimated light beam propagating through the light guideplate 121 through the total reflection a plurality of times, and emitsthe collimated light beam, as it is, from the first face 122 of thelight guide plate 121. However, without being limited to theabove-described configuration, the second face 123 may be the incidentface of the light guide plate, and the first face 122 may be theemission face of the light guide plate. Further, the diffraction gratingmember may be provided on (adhered to) the light guide plate so that thefirst first photosensitive material layer of the hologram recording filmfaces the second face 123 of the light guide plate 121. Otherwise, thediffraction grating member may be provided on (adhered to) the lightguide plate so that the M-th first photosensitive material layer of thehologram recording film faces the second face 123 of the light guideplate 121.

In the fifth embodiment, each of the first and second diffractiongrating members 130 and 140 includes P (where the equation P=3 holds andthe number 3 denotes three types of colors including red, green, andblue) photosensitive material layers that are laminated on one another,so as to be ready for the diffraction and reflection of P types of lightbeams having P types of wavelength bands (and/or wavelengths). Theinterference fringes corresponding to a single type of wavelength band(and/or wavelength) are formed on each of the photosensitive materiallayers including a photopolymer material, and the photosensitivematerial layers are generated according to the methods described in thefirst to third embodiments. The surface pitch of the interferencefringes formed on each of the P types of photosensitive material layersis constant in each of the wavelength bands, and the interferencefringes are linear and parallel with the Z-axis direction. In each ofFIGS. 10A and 12, each of the first and second diffraction gratingmembers 130 and 140 is shown as a single layer. Through the use of theabove-described configuration, it becomes possible to increase thediffraction efficiency and the diffraction reception angle, and optimizethe diffraction angle when the light beams with the individualwavelength bands (and/or wavelengths) are diffracted and reflected inthe first and second diffraction grating members 130 and 140.

Namely, the collimated light beams of the three colors including red,green, and blue propagate through the light guide plate 121 through thetotal reflection and are emitted. Since the light guide plate 121 isthin and the optical path inside the light guide plate 121, throughwhich the collimated light beams propagate, is long, the number of thetotal reflections attained until the collimated light beams reaches thesecond diffraction grating member 140 is varied based on each angle ofview. More specifically, of the collimated light beams that are madeincident on the light guide plate 121, the reflection number of acollimated light beam which is made incident at an angle taking adirection toward the second diffraction grating member 140 is smallerthan that of a collimated light beam which is made incident at an angletaking a direction away from the second diffraction grating member 140.This is because the angle which a collimated light beam that isdiffracted and reflected in the first diffraction grating member 130 andthat is made incident on the light guide plate 121 at an angle taking adirection toward the second diffraction grating member 140 forms with anormal of the light guide plate 121 when the collimated light beampropagating through the light guide plate 121 collides with the insidesurface of the light guide plate 121 is smaller than the angle which acollimated light beam which is made incident on the light guide plate121 at an angle reverse to the above-described angle, that is, an angleaway from the second diffraction grating member 140, forms with thenormal of the light guide plate 121. The form of the interferencefringes generated inside the second diffraction grating member 140 andthat of the interference fringes generated inside the first diffractiongrating member 130 are symmetric with respect to a virtual faceperpendicular to the axis of the light guide plate 121.

In the first embodiment, the image forming device 111 includes areflection-type spatial light modulation device 150 and a light source153 including a light-emitting diode emitting a white color beam. Morespecifically, the reflection-type spatial light modulation device 150includes a liquid crystal display (LCD) 151 including the LCOSfunctioning as the light valve and a polarization beam splitter 152 thatreflects part of the light beam emitted from the light source 153, leadsthe reflected light beam to the LCD 151, makes part of the light beamreflected by the LCD 151 pass through, and leads the light beam to thecollimating optical system 112. The LCD 151 includes a plurality of(e.g., 320×240) pixels (liquid crystal cells) that are arranged in atwo-dimensional matrix form. The polarization beam splitter 152 has aconfiguration and a structure according to a related art. Anon-polarized light beam emitted from the light source 153 collides withthe polarization beam splitter 152. A P-polarized component passesthrough the polarization beam splitter 152 and emitted from the system.On the other hand, an S-polarized component is reflected in thepolarization beam splitter 152, made incident on the LCD 151, reflectedinside the LCD 151, and emitted from the LCD 151. Of the light beamsemitted from the LCD 151, a light beam emitted from a pixel displaying“white” includes many P-polarized components, and a light beam emittedfrom a pixel displaying “black” includes many S-polarized components.Therefore, of the light beams that are emitted from the LCD 151 and thatcollide with the polarization beam splitter 152, the P-polarizedcomponent passes through the polarization beam splitter 152 and is ledto the collimating optical system 112. On the other hand, theS-polarized component is reflected in the polarization beam splitter 152and returned to the light source 153. The LCD 151 includes a pluralityof (e.g., 320×240) pixels (the number of liquid crystal cells is threetimes larger than the pixel number) that are arranged in atwo-dimensional matrix form, for example. The collimating optical system112 includes, for example, a convex lens, and the image forming device111 (more specifically, the LCD 151) is arranged at the place (position)of a focal length defined in the collimating optical system 112 so as togenerate a collimated light beam. Here, a single pixel includes a redlight emitting sub-pixel emitting a red light beam, a green lightemitting sub-pixel emitting a green light beam, and a blue lightemitting sub-pixel emitting a blue light beam.

In the fifth embodiment and/or a sixth embodiment, which will bedescribed later, the light guide plate 121 including optical glassand/or a plastic material has two parallel faces (the first and secondfaces 122 and 123) extending in parallel with the axis of the lightguide plate 121. The first face 122 and the second face 123 are opposedto each other. The collimated light beam is made incident on the firstface 122 corresponding to the light incident face, propagates throughthe light guide plate 121 through the total reflection, and is emittedfrom the second face 123 corresponding to the light emission face.Without being limited to the above-described configuration, the secondface 123 may be provided as the light incident face and the first face122 may be provided as the light emission face.

FIG. 11 is a conceptual illustration showing the state where a pair ofthe image display apparatuses of the fifth embodiment is worn by a user,as the HMD. The use of the image display apparatuses according to thefifth embodiment allows for reducing the weight and the size of the HMD,significantly reducing user discomfort caused by the HMD mounted on theuser's head, and reducing the manufacturing cost.

Sixth Embodiment

The sixth embodiment in an embodiment relates to an image displayapparatus 200 according to the second mode. The image display apparatus200 includes:

(A) a light source 251,

(B) a collimating optical system 252 making a light beam emitted formthe light source 251 into a collimated light beam,

(C) a scanning unit 253 configured to scan the collimated light beamemitted from collimating optical system 252,

(D) a relay optical system 254 configured to relay the collimated lightbeam scanned through the scanning unit 253, and

(E) an optical device 120 onto which the above-described collimatedlight beam is made incident, in which the collimated light beam isguided, and from which the collimated light beam is emitted through therelay optical system 254,

as shown in a conceptual illustration of FIG. 12. Since the opticaldevice 120 has the same configuration and structure as those of theoptical device 120 described in the fifth embodiment, the detaileddescription thereof will be omitted.

The light source 251 includes a red light emitting element 251R emittinga red light beam, a green light emitting element 251G emitting a greenlight beam, and a blue light emitting element 251B emitting a blue lightbeam, and each of the light emitting elements includes a semiconductorlaser element. The light beams of three primary colors, which areemitted from the light source 251, pass through a cross prism 255 sothat the color synthesis is achieved, the optical paths of the lightbeams are assembled into a single optical path, and the light beams aremade incident on the collimating optical system 252 having a positiveoptical power on the whole and emitted from the collimating opticalsystem 252 as a collimated light beam. The above-described collimatedlight beam is reflected by a total reflection mirror 256, and subjectedto horizontal scanning and vertical scanning through the scanning unit253 that includes the MEMS including a micromirror which can be freelyrotated in a two-dimensional direction and that can scan the incidentcollimated light beam two-dimensionally. Consequently, the collimatedlight beam is made into a type of two-dimensional image and at least onevirtual pixel is generated. Then, a light beam emitted from the virtualpixel passes through the relay optical system 254 including a relayoptical system according to a related art, and is made into a collimatedlight beam. The collimated light beam is made incident on the opticaldevice 120.

Thus, the present application has been explained based on theabove-described embodiments. However, the present invention can beachieved without being limited to the above-described embodiments. Theconfiguration and structure of each of the hologram recording films, thelaminated structures, and the image display apparatuses according to theabove-described embodiments are exemplarily described. The configurationand structure can, therefor, be modified appropriately. For example, theoptical device described in the fifth embodiment and/or the sixthembodiment may include a first polarization unit having atransmission-type hologram, which is provided on the first face 122 ofthe light guide plate 121, in place of the first diffraction gratingmember 130, and the second diffraction grating member 140 having areflection-type hologram, which is provided on the second face 122.According to the above-described configuration, a light beam which ismade incident on the first polarization unit is diffracted, satisfiesthe total reflection condition inside the light guide plate 121, andpropagates to the second diffraction grating member 140. Then, the lightbeam is diffracted and reflected by the second diffraction gratingmember 140, and emitted from the light guide plate 121. Otherwise, afirst polarization unit functioning as a reflecting mirror may beprovided in the light guide plate 121 in place of the first diffractiongrating member. The above-described first polarization unit may include,for example, a light reflection film (a type of mirror) that has a metalincluding an alloy and that reflects a light beam which is made incidenton the light guide plate 121 and/or a diffraction grating (e.g., ahologram diffraction grating film) configured to diffract the light beamwhich is made incident on the light guide plate 121. Otherwise, a secondpolarization unit functioning as a semitransparent mirror may beprovided in the light guide plate 121 in place of the second diffractiongrating member. The above-described second polarization unit mayinclude, for example, a multilayer laminated structure including a largenumber of dielectric lamination films that are laminated on one another,a half mirror, a polarization beam splitter, and a hologram diffractiongrating film. Otherwise, the first polarization unit including thetransmission-type hologram may be replaced with a combination of atransmission-type LCD and a free form surface lens.

Further, the hologram recording film manufacturing method according tothe second mode can be used in place of the hologram recording filmmanufacturing method according to the first mode. Namely, when thelaminated structure is irradiated with an energy ray from the laminatedstructure's one face side at step (C), the regions of the laminatedstructure may be irradiated with energy rays with different energyamounts so as to make the slant angles observed in the regions of thelaminated structure different from each other while retaining the valueΛ of the surface pitch. Further, the laminated structure may include notonly the first and second photosensitive material precursor layers, butalso the first to third photosensitive material precursor layers, or thefirst to fourth photosensitive material precursor layers.

As an exemplary modulation of the image forming device according to thefirst embodiment, an active matrix-type image forming device shown in aconceptual illustration of FIG. 13 may be exemplarily provided. Theactive matrix-type image forming device includes a light emitting panelhaving light emitting elements 301, where each of the light emittingelements 301 includes a semiconductor light emitting element, that arearranged in a two-dimensional matrix form. The active matrix-type imageforming device displays an image by controlling the lightemission/non-light emission state of each of the light emitting elements301 so that the light emission state of each of the light emittingelements 301 is visually identified in a direct manner. A light beamemitted from the above-described image forming device is made incidenton the light guide plate 121 via the collimating optical system 112.

Otherwise, as shown in a conceptual illustration of FIG. 14, an imageforming device configured to display a color image includes:

(α) a red light emitting panel 311R including red light emittingelements 301R emitting red light beams, where the red light emittingelements 301R are arranged in a two-dimensional matrix form,

(β) a green light emitting panel 311G including green light emittingelements 301G emitting green light beams, where the green light emittingelements 301G are arranged in a two-dimensional matrix form,

(γ) a blue light emitting panel 311B including blue light emittingelements 301B emitting blue light beams, where the blue light emittingelements 301B are arranged in a two-dimensional matrix form, and

(δ) a unit provided to bring together the light beams that are emittedfrom the red light emitting panel 311R, the green light emitting panel311G, and the blue light emitting panel 311B into a single optical path(e.g., a dichroic prism 303),

wherein the light emission/non-light emission state of each of the redlight emitting panel 311R, the green light emitting panel 311G, and theblue light emitting panel 311B is controlled. The light beams emittedfrom the above-described image forming device are also made incident onthe light guide plate 121 via the collimating optical system 112. Here,reference numeral 312 denotes a microlens configured to collect thelight beams emitted from the light emitting elements.

FIG. 15 is a conceptual illustration of an image forming deviceincluding light emitting panels 311R, 311G, 311B, and so forth in whichlight emitting elements 301R, 301G, and 301B are individually arrangedin a two-dimensional matrix form. The passage and/or the non-passage oflight beams emitted from the light emission panels 311R, 311G, and 311Gis controlled through individual light passage control devices 304R,304G, and 304B. The light beams are made incident on the dichroic prism303 and the optical paths of the light beams are assembled into a singleoptical path. The light beams are made incident on the light guide plate121 via the collimating optical system 112.

FIG. 16 exemplarily shows another conceptual illustration of the imageforming device including the light emitting panels 311R, 311G, 311B, andso forth in which the light emitting elements 301R, 301G, and 301B areindividually arranged in a two-dimensional matrix form. Light beamsemitted from the light emitting panels 311R, 311G, and 311B are madeincident on the dichroic prism 303 and the optical paths of the lightbeams are assembled into a single optical path. The passage and/or thenon-passage of each of the light beams emitted from the dichroic prism303 is controlled through the light passage control device 304, and thelight beams are made incident on the light guide plate 121 via thecollimating optical system 112.

FIG. 17 exemplarily shows an image forming device including the lightpassage control device 304R (e.g., a liquid crystal display device)which is a type of light valve configured to control the red lightemitting element 301R, and the passage and/or the non-passage of a lightbeam emitted from the red light emitting element 301R, the light passagecontrol device 304G (e.g., a liquid crystal display device) which is atype of light valve configured to control the green light emittingelement 301G, and the passage and/or the non-passage of a light beamemitted from the green light emitting element 301G, the light passagecontrol device 304B (e.g., a liquid crystal display device) which is atype of light valve configured to control the blue light emittingelement 301B, and the passage and/or the non-passage of a light beamemitted from the blue light emitting element 301B, a light guide member302 configured to guide the light beams that are emitted from theabove-described light emitting elements 301R, 301G, and 301B, where eachof the above-described light emitting elements 301R, 301G, and 301Bincludes a gallium nitride (GaN)-based semiconductor, and a unitconfigured to assemble the optical paths of the light beams into asingle optical path (e.g., the dichroic prism 303).

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope and without diminishing itsintended advantages. It is therefore intended that such changes andmodifications be covered by the appended claims.

The application is claimed as follows:
 1. A hologram recording filmcomprising: a multilayer structure in which M (where M≧2)photosensitive-material layers made of a photosensitive material and atleast one (M−1) resin layer are alternately stacked, thephotosensitive-material layers having interference fringes with adesired pitch and slant angle, the resin layer having a different energyray transmittance or energy ray transmission amount from thephotosensitive-material layers, wherein among the Mphotosensitive-material layers, values of pitches are identical andslant angles are different on surfaces of the photosensitive-materiallayers, and the resin layer is composed of an (M−1)second-photosensitive-material layer made of a second photosensitivematerial, the second-photosensitive-material layer having interferencefringes with a desired pitch and slant angle.
 2. The hologram recordingfilm according to claim 1, wherein the resin layer enables slant anglesin the individual photosensitive-material layers to be controlled. 3.The hologram recording film according to claim 1, wherein the resinlayer contains a material that absorbs an energy ray.
 4. The hologramrecording film according to claim 1, wherein a reproduction centerwavelength in the M photosensitive-material layers is changed inaccordance with a value of M.
 5. The hologram recording film accordingto claim 4, wherein a difference between a reproduction centerwavelength before irradiation of an energy ray and a reproduction centerwavelength after irradiation of an energy ray changes more monotonouslyas the value of M increases.
 6. An image display device comprising: (A)an image forming device including a plurality of pixels arranged in atwo-dimensional matrix pattern; (B) a collimating optical systemconfigured to collimate light beams emitted from the individual pixelsof the image forming device; and (C) an optical device configured toreceive, guide, and emit the light beams collimated by the collimatingoptical system, the optical device including (a) a light guiding plateconfigured to receive the light beams, cause the light beams topropagate therein by total reflection, and emit the light beams, (b) afirst diffraction grating member provided on the light guiding plate andconfigured to diffract and reflect the light beams received by the lightguiding plate so that the light beams received by the light guidingplate are totally reflected in the light guiding plate, and (c) a seconddiffraction grating member provided on the light guiding plate andconfigured to diffract and reflect the light beams propagated in thelight guiding plate by total reflection and cause the light beams to beemitted from the light guiding plate, wherein the first diffractiongrating member and the second diffraction grating member are composed ofa hologram recording film, the hologram recording film includes amultilayer structure in which M (where M≧2) photosensitive-materiallayers made of a photosensitive material and at least one (M−1) resinlayer are alternately stacked, the photosensitive-material layers havinginterference fringes with a desired pitch and slant angle, the resinlayer having a different energy ray transmittance or energy raytransmission amount from the photosensitive-material layers, among the Mphotosensitive-material layers, values of pitches are identical andslant angles are different on surfaces of the photosensitive-materiallayers, and the resin layer is composed of an (M−1)second-photosensitive-material layer made of a second photosensitivematerial, the second-photosensitive-material layer having interferencefringes with a desired pitch and slant angle.
 7. An image display devicecomprising: (A) a light source; (B) a collimating optical systemconfigured to collimate light emitted from the light source; (C)scanning means for scanning collimated light emitted from thecollimating optical system; (D) a relay optical system configured torelay the collimated light scanned by the scanning means; and (E) anoptical device configured to receive, guide, and emit the lightcollimated by the relay optical system, the optical device including (a)a light guiding plate configured to receive the light, cause the lightto propagate therein by total reflection, and emit the light, (b) afirst diffraction grating member provided on the light guiding plate andconfigured to diffract and reflect the light received by the lightguiding plate so that the light received by the light guiding plate istotally reflected in the light guiding plate, and (c) a seconddiffraction grating member provided on the light guiding plate andconfigured to diffract and reflect the light propagated in the lightguiding plate by total reflection and cause the light to be emitted fromthe light guiding plate, wherein the first diffraction grating memberand the second diffraction grating member are composed of a hologramrecording film, the hologram recording film includes a multilayerstructure in which M (where M≧2) photosensitive-material layers made ofa photosensitive material and at least one (M−1) resin layer arealternately stacked, the photosensitive-material layers havinginterference fringes with a desired pitch and slant angle, the resinlayer having a different energy ray transmittance or energy raytransmission amount from the photosensitive-material layers, among the Mphotosensitive-material layers, values of pitches are identical andslant angles are different on surfaces of the photosensitive-materiallayers, and the resin layer is composed of an (M−1)second-photosensitive-material layer made of a second photosensitivematerial, the second-photosensitive-material layer having interferencefringes with a desired pitch and slant angle.
 8. The image displaydevice according to claim 6, wherein the resin layer enables slantangles in the individual photosensitive-material layers to becontrolled.
 9. The image display device according to claim 6, whereinthe resin layer contains a material that absorbs an energy ray.
 10. Theimage display device according to claim 6, wherein a reproduction centerwavelength in the M photosensitive-material layers is changed inaccordance with a value of M.
 11. The image display device according toclaim 10, wherein a difference between a reproduction center wavelengthbefore irradiation of an energy ray and a reproduction center wavelengthafter irradiation of an energy ray changes more monotonously as thevalue of M increases.